The objective of this research is to isolate and identify chemical species containing arsenic, as they occur in living organisms. Initially, algae and crayfish will be used as the experimental organisms from which arsenic compounds will be isolated. This is because techniques have already been developed for the separation of arsenic-containing compounds from these organisms. As knowledge concerning the chemical nature of the arsenic species is acquired, it will become feasible to extend this study to include higher animals. The ultimate goal of this work is to determine the manner in which arsenic becomes incorporated in the mammal. Such knowledge may make it possible to begin to learn about the true toxicity of arsenic and its compounds, and whether arsenic may, in fact, be an essential trace element. Initially, crayfish and algae will be cultivated in an environment which contains arsenate and/or arsonite traced with 74As (t 1/2 18d). The cells will be homogenized and subjected to classical biochemical separation procedures. Protein, lipid, carbohydrate and nucleic acid fractions will be separated. The fractions will be subjected to chromatographic purification. Arsenic rich fractions will be identified by way of their 74As activity. The arsenic-containing fractions will be subjected to additional chromatographic and electrophoretic methods. Initial characterization of the arsenic compounds will utilize mass spectroscopy, as well as Laser Raman, infrared, photo-electron spectroscopy, and gas chromatography. This will be followed by proof-of-structure studies by chemical means.